Quarterly report pursuant to Section 13 or 15(d)

Debt and Secured Revolving Line of Credit (Narrative) (Details)

v3.8.0.1
Debt and Secured Revolving Line of Credit (Narrative) (Details)
3 Months Ended
Sep. 14, 2016
USD ($)
day
$ / shares
Apr. 14, 2015
USD ($)
Mar. 31, 2018
USD ($)
Apr. 01, 2017
USD ($)
Mar. 29, 2018
$ / shares
Dec. 30, 2017
USD ($)
Dec. 31, 2016
USD ($)
Sep. 28, 2016
USD ($)
Jun. 16, 2014
USD ($)
Feb. 26, 2014
USD ($)
Aug. 15, 2012
USD ($)
Debt Instrument [Line Items]                      
Aggregate principal amount repurchased [1],[2]     $ 14,000,000 $ 0              
Secured Revolving Line of Credit                      
Debt Instrument [Line Items]                      
Secured revolving line of credit, outstanding balance     $ 70,000,000     $ 70,000,000          
Secured revolving line of credit, interest rate     5.00%     4.75%          
Letters of credit outstanding, amount     $ 31,000,000                
Secured revolving line of credit, remaining borrowing capacity     $ 149,000,000                
Repayment period     90 days                
Secured Revolving Line of Credit | Amended and restated loan and security agreement                      
Debt Instrument [Line Items]                      
Maximum borrowing capacity   $ 500,000,000                  
Maximum letters of credit available for issuance   45,000,000                  
Aggregate amount by which size of commitments may be increased (up to)   $ 200,000,000                  
Secured Revolving Line of Credit | Amended and restated loan and security agreement | Federal Funds Rate                      
Debt Instrument [Line Items]                      
Basis spread on variable rate   0.50%                  
Secured Revolving Line of Credit | Amended and restated loan and security agreement | LIBOR                      
Debt Instrument [Line Items]                      
Basis spread on variable rate   1.00%                  
2.125% Convertible Senior Notes due 2026                      
Debt Instrument [Line Items]                      
Stated interest rate 2.125%                    
Principal $ 700,000,000   $ 805,000,000     $ 805,000,000   $ 105,000,000      
Conversion ratio     0.1250031                
Initial conversion price (in dollars per share) | $ / shares $ 8.00                    
Fundamental change repurchase price, percent of principal amount 100.00%                    
Debt issuance costs             $ 15,000,000        
Equity issuance costs     $ 9,000,000       $ 9,000,000        
Remaining life     102 months                
Share price (in usd per share) | $ / shares         $ 10.05            
If-converted value in excess of principal     $ 206,000,000                
Effective interest rate     8.00%                
2.125% Convertible Senior Notes due 2026 | Debt Instrument, circumstance 1                      
Debt Instrument [Line Items]                      
Threshold trading days | day 20                    
Threshold consecutive trading days | day 30                    
Threshold percentage of conversion price 130.00%                    
2.125% Convertible Senior Notes due 2026 | Debt Instrument, circumstance 2                      
Debt Instrument [Line Items]                      
Threshold consecutive trading days | day 10                    
Threshold percentage of conversion price 98.00%                    
Conversion period after threshold period days | day 5                    
6.75% Senior Notes due 2019                      
Debt Instrument [Line Items]                      
Stated interest rate                   6.75%  
Principal                   $ 600,000,000  
Aggregate principal amount repurchased     $ 14,000,000                
Outstanding aggregate principal amount     153,000,000                
7.50% Senior Notes due 2022                      
Debt Instrument [Line Items]                      
Stated interest rate                     7.50%
Principal                     $ 500,000,000
Outstanding aggregate principal amount     347,000,000                
7.00% Senior Notes due 2024                      
Debt Instrument [Line Items]                      
Stated interest rate                 7.00%    
Principal                 $ 500,000,000    
Outstanding aggregate principal amount     $ 311,000,000                
[1] Amounts reflected adoption of ASU 2016-18, Statement of Cash Flows, Restricted Cash (Topic 230) beginning in the first quarter of 2018.
[2] Prior year amounts adjusted to reflect the retrospective application of ASU 2014-09, Revenue from Contracts with Customers. Refer to Note 1.